Translating device



1931- R. w. CARLISLE ETAL 1,837,755

TRANSLATING DEVICE Filed June 22, 1929 2'Sheets-Sheet 1 INVENTOR Richard WCarZz's-Ze &, Israel 5. Pierso ATTORNEY Dec. 22, 1931.

R. W. CARLISLE ET AL v TRANSLATING DEVICE Filed June 22, 1929 2 Sheets-Sheet 2 Fig. 3.

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r ATTORNEY INVENTOR Richard W Carlz'sl e [sra Z 6'. Pier on.

Patented Dec. 22, 1931 UNITED STATES RICHARD W. CARLISLE, OF PITTSBURGH, PENNSYLVANIA, AND ISRAEL S. PIERSON, OI

PATENT OFFICE SCI-IENECTADY, NEW YORK; SAID CABLISLE ASSIGNOR TO WESTINGHOUSE ELEC- TRIO AND MANUFACTURING COMPANY, A CORPORATION OF IENNSYLVANIA, AND

SAID PIERSON ASSIGNOR TO GENERAL ELECTRIC COMPANY, A, CORPORATION 01 NEW YORK TBANSLATING DEVICE Application filed June 22,

telephone receivers of the type commonly known as loud speakers wherein the vibratile diaphragm is a large freely suspended cone.

There has been a recent tendency toward the equipping of hotel rooms and rooms in private residences with loud speakers that are permanently built into the walls of the rooms. In such event, it is desirable that the rear of the loud speaker shall be completely enclosed in order that dust, dirt, moisture, etc., shall not cause deterioration of the actuating mechanism. Unfortunately, however, the complete enclosing of the rear of the loud speaker gives rise to undesirable resonance phenomena, the diaphragm compartment constituting a resonator of the Helmholz type which unduly accentuates some particular one of the vibration frequencies of the diaphragm.

Efiorts have been made to devise wall-type loud speakers that should be devoid of resonance phenomena, but, insofar as We are aware, no loud speaker of this type, constructed previous to our invention, has been entirely satisfactory.

It is, accordingly, an object of our invention to provide a loud speaker of the Wall type that shall be free from resonance phenomena.

Another object of our invention is to provide mounting means for a translating device of either the telephone-transmitter or the telephone-receiver type, whereby resonance phenomena shall be minimized.

Another and more specific object of our invention is to provide, in a loud speaker comprising a large conical diaphragm, means whereby resonance phenomena are prevented.

In constructing a loud-speaker according to our invention, we mount a diaphragm and the attendant actuating mechanism therefor in a substantially closed compartment, hereinafter known as the diaphragm compartment, and provide another closed compart- 1929. Serial No. 372,879.-

ment which A communicates with the diaphragm compartment by means of a restrict ed air passage. The term restricted is chosen to indicate that the air passage is either tortuous or is provided with impedance means, such as felt or the like, whereby the free interchange ofv air between the two compartments is hindered.

-The diaphragm and the diaphragm com- A partment constitute an oscillatory system that is resonant to a definite frequency. The dimensions of the second compartment are so chosen that it is also resonant to the same frequency. The entire device, therefore, comprlses two oscillatory systems that are coupled together and'are critically damped by the impedance means in the communi catin passage.

The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims. The 1nvention itself, however, both as to its organization and its method of operation, togetherwith additional objects and advantages thereof, will best be understood from the following description of several specific embodiments, when read in connection with the accompanying drawings in which:

Figure 1 is an elevational view of a loud speaker of the wall type comprising a preferred embodiment of our invention;

Fig. 2 is an elevational view, partly in cross-section, of the device shown in Fig. 1, the section being taken along'a line corre sponding to the line 11-11 in Fig. 1;

Figs. 3, 4, 5 and 6 are elevational views, partly in cross-section, of alternative forms of our invention; and

Fig. 7 is a circuit diagram to which referconnected to the apex of the cone through an element 5 of any preferred form.

A plurality of bolts 6 extend through openings in the periphery of the pan-shaped element and serve to clamp a diaphragm-mounting annulus 7 of flexible material tightly thereto. A fiat metallic ring 8 is preferably interposed between the headsof the bolts 6 and the annulus 7 and, if desired, a plurality of semi-resilient gaskets 10 may be disposed at each side of the ring.

A plurality of bolts 11 extend through openings in the periphery of the pan-shape element and serve to clamp the loud-speaker assembly firmly against the rear surface of an ornamental cover plate 12. The last-mentioned bolts 11 also function to clamp a cylindrical bafile element 17 firmly against the rear surface of the periphery of the panshape element 2 and to maintain it coaxial therewith.

The complete loud-speaker assembly constituted by the diaphragm, the pan-shape element, the motor, the cover plate and the cylindrical bafile element, is so disposed coaxially of a cup-shape metallic box 13 that the inner end of the cylindrical element is spaced a short distance forwardly of the bottom of the said box.

A ring 14 of felt or similar material is mounted exteriorly of the inner cylindrical element and is so disposed as to close the circular air-passage that otherwise would be defined between the inner end of the said cylingrical element and the bottom of the metallic The loud-speaker assembly is preferably held in position within the metallic box by means of a plurality of bolts 15 or the like, which extend through plain openings in the cover-plate, into threaded openings provided in an inturned edge of the metallic box.

The principle on which the operation of our improved translating device is based is probably best explained by comparing it to an electrical circuit. By reason of physical relationship between the several elements constituting our device, its action may be studied by comparing it to the circuit network shown in Fig. 7 wherein C, represents the apparent restoring-force or compliance of the cone; M

represents the mass of the cone; R represents the radiation resistance of the cone; C rep resents the compliance of the air in the diaphragm compartment; M represents the inertance of the air in the communicating passage between the several compartments; while R representsthe resistance coefficient of the passageway and C stands for the compliance of the communicating or extra compartment.

It is believed to be apparent that, if the felt were omitted from the communicating passage, the air, in passing therethrough when the cone is caused to vibrate, wou d have a much higher velocity than it would have when moving in either of thecompartments. The energy of vibration in the air, therefore, is much more efficiently dissipated by interposing the dissipative agent, namely, the felt, in the passage than it would be if the felt were disposed in either of the compartments.

The device is accordingly seen to be the equivalent of two coupled oscillatoig circuits, one circuit being comprising 0,, R, and Cdfi, the other circuit comprising G M B0 and C the two circuits hem coupled through the compliance O of the iaphragm compartment. When these two systems are resonant to the same frequency, f, and when 1 1/ R, X R, 2,30

both oscillatory systems are criticall damped, and resonance phenomena in both are prevented.

Since the derivation of the above formulae may be found in substantially any standard text book dealing with resonant circuits, it need not be iven in detail at this point.

It is therefbre, apparent that the amount of damping in the passage between the compart ments, R and the inertance of the air in the passageway, M,,, can be so adjusted that neither compartment will oscillate or resonate.

In the event that insufficient damping is obtained by the use of a single extra compartment, such as illustrated in Figs. 1, 2 and 3, a plurality of resonant compartments may be provided, as shown in Fig. 4. In the event that more than one com artment is used, passageways are provid dd between the neighboring compartments, each passa 8- way having a dampin element 16 so isposed with reference t ereto as to impede the free flow of air between the several compartments.

Theoretically, there is no limit to the number of resonant compartments that may be provided, but, from a practical standpoint, It is not economical to build the cabinet with more than one or two compartments.

It also lies within the scope of our invention to dispense with a s ecific opening between compartments and to, instead, construct the partitions of a porous material, such as celotex, or the like. In such event, sufficient dampmg is obtained by the pass ing of the air through the interstices of the partition.

In certain instances, fairly satisfactory damping may be obtained by merely providing a restricted opening in the diaphragm compartment, as illustrated in Fig. 5, and by disposing damping material to impede the passage of air through the said opening.

The device shown m Fig. 5 may be modified by the addition of one or more damping compartments, as shown in Fig. 6, the last compartment opening into the surrounding air, rather than being closed as illustrated in Figs. 1 to 4 inclusive.

Our invention is also applicable to telephone transmitters, of the type shown in the patent to Thomas 1,569,411, for example, in order that resonance phenomena in an enclosing casing shall be eliminated.

Numerous other modifications of the spe cific embodiments of our invention chosen for illustration will be apparent to those skilled in the art to which it pertains. Our invention, therefore, is not to be limited except in so far as is necessitated by the prior art or by the spirit of theappended claims.

We claim as our invention:

1. In a translating .device, a diaphragmcompartment, a compartment communicating therewith, and means for reducing resonance phenomena in said compartments.

2. In a translating device, a diaphragmcompartment, a compartment communicating therewith, and means for increasing the resistance to the passage of air between said compartments, whereby resonance phenomena may be substantially prevented.

3. In an acoustic translating device, a diaphragm compartment, a plurality of compartments communicating therewith by oriflees in tandem, and means for damping resonances in the diaphragm and in the chamhers communicating therewith, said means consisting of felt or similar dissipative material disposed in at least one region in which the air has a high velocity as compared with its velocity in nearby regions.

4. In a translating device, a resonant diaphragm-compartment, a resonant compart ment communicating therewith, and means for damping the development of resonance phenomena in said'compartments.

5. In a translating device, a vibratile dia phragm, a diaphragm compartment at least partially enclosing said diaphragm and being resonant to a vibration frequency there-- of, a second compartment, and means comprising a partially obstructed air passage joining said compartments.

6. In a translating device, a vibratile diaphragm, a diaphragm-compartment at least partially enclosing said diaphragm and being resonant to a vibration frequency thereof, means comprising a communicating compartment and vibration damping means between said two compartments for preventing the development of resonance phenomena in said diaphragm compartment.

7. In a translating device, a vibratile diaphragm, a diaphragm-compartment resonant to a vibration frequency of said diaphragm, a second compartment resonant to approximately the same frequency, and impedance coupling means between said compartments for securing critical damping of resonance phenomena.

8. In a translating system, a vibratile diaphragm, a diaphragm compartment resonant to a vibration frequency of said diaphragm,

and means for critically damping the system,

whereby resonance phenomena 'at the said vibration frequency are minimized.

9. In a translating system, a vibratile diaphragm, a diaphragm compartment, a second compartment, a communicating passage between said compartments, the resonant frequency of the second compartment being substantially the same as that of diaphragm in combination with the diaphragm compartment, and damping means associated with said passage for preventing the occurrence of resonance phenomena in either compartment and in said diaphragm.

10. In a loud-speaker, reproducing mechanism comprising a motor and a diaphragm, a canopy surrounding said mechanism, an enclosure surrounding said canopy and said mechanism, said canopy extending to within a short distance of a rear wall of said enclosure, and damping material interposed between and bridging the opening between said rear wall and said canopy.

11. In a translating device, a cabinet having a plurality of compartments, restricted passages between adjacent compartments, and damping material associated with said passages, the resonant frequency of the compartments being substantially the same, whereby resonance phenomena are minimized.

In testimony whereof, we have hereunto subscribed our names this 23rd day of May, 1929, and this 10th day of June, 1929, respectively,

RICHARD W. CARLISLE. ISRAEL S. PIERSON. 

